Lesions 367 



of the testicle being more common than of the uterus or 

 ovaries. 



Wounds are also occasional avenues of entrance for 

 tubercle bacilli. Anatomic tubercles are not uncommon 

 upon the hands of anatomists and pathologists, most of 

 these growths being tuberculous in nature. Such dermal 

 lesions usually contain few bacilli. 



Lesions. The macroscopic lesions of tuberculosis are too 

 familiar to require a description of any considerable length. 

 They consist of nodules, or collections of nodules, called 

 tubercles, irregularly scattered through the tissues, which 

 are more or less disorganized by their presence and retro- 

 gressive changes. 



When tubercle bacilli are introduced beneath the skin of 

 a guinea-pig, the animal shows no sign of disease for a 

 week or two, then begins to lose appetite, and gradually 

 diminishes in flesh and weight. Examination usually shows 

 a nodule at the point of inoculation and enlargement of the 

 neighboring lymphatic glands. The atrophy increases, the 

 animal shows a febrile reaction, and dies at the end of a 

 period of time varying from three to twelve weeks. Post- 

 mortem examination usually shows a cluster of tubercles 

 at the point of inoculation, tuberculous enlargement of 

 lymphatic glands both near and remote from the primary 

 lesion, and a widespread tuberculous invasion of the lungs, 

 liver, kidneys, peritoneum, and other organs. Tubercle 

 bacilli are demonstrable in immense numbers in all the 

 invaded tissues. The disease in the guinea-pig is usually 

 more widespread than in other animals because of its greater 

 susceptibility, and the death of the animal occurs more 

 rapidly for the same reason. Intraperitoneal injection of 

 tubercle bacilli in guinea-pigs causes a still more rapid dis- 

 ease accompanied by widespread lesions of the abdominal 

 organs. The animals die in from three to six weeks. In 

 rabbits the disease runs a longer course with similar lesions. 

 In cattle and sheep the infection is commonly first seen in 

 the alimentary apparatus and associated organs, and may 

 be limited to them though primary pulmonary disease also 

 occurs. In man, the disease is chiefly pulmonary, though 

 gastro-intestinal and general miliary tuberculosis is com- 

 mon. The development of the lesions in whatever tissue or 

 animal always depends upon the distribution of the bacilli 

 by the lymph or the blood. 



